Container

ABSTRACT

A package is provided with a lid and container that are heat sealed together. A multi-ply sheet material is provided for being thermoformed to define the container which has a tapering wall and bulge-resistant bottom end. Prior to thermoforming the container from the sheet, the sheet is heated with oval pads on a plurality of plates which are arranged in a configuration to facilitate control of the sheet temperature. A plug is used in the thermoforming process to contact the sheet and position the sheet within a die. A lid sheet is heat sealed to the container sheet over the thermoformed containers so as to produce a pair of spaced-apart, annular bead heat seals. The package is completed by severing the sealed-together sheets at the periphery of the container with a punch and die set that produces and clean, smooth cut surface.

CROSS REFERENCE TO RELATED APPLICATION(S)

[0001] Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

REERENCE TO A MICROFICHE APPENDIX

[0003] Not applicable.

TECHNICAL FIELD

[0004] The present invention relates to a container and lid which areformed from separate webs of sheet material. The invention furtherrelates to a method and apparatus for heating the container sheetmaterial, for forming the container, for hermetically sealing the lid tothe container after the container is filled with a product, and forpunching the sealed lid and container from the webs of sheet material.

BACKGROUND OF THE INVENTION AND TECHNICAL PROBLEMS POSED BY THE PRIORART

[0005] Various packages are in use or have been proposed for containinga product, such as a food product or medical product, wherein thepackage is hermetically ed until it is opened for use. One type ofconventional package typically includes a cup or container comprising ahollow body so having an opening or mouth surrounded by a flange towhich a lid is heat sealed. While such packages function generallysatisfactorily, it would be desirable to provide an improved packagewhich could be more readily manufactured, which could be more easilyused, and which would provide advantages and features not heretoforerealized. For example, it is desirable to provide a container that canbe opened readily and that can be used as a drinking glass.

[0006] Although packages comprising a cup and peel-away lid offerconvenience of use, such packages are typically made from a relativelythin, thermoplastic sheet material. Such thin sheet material may becharacterized as a web, film, sheet, sheet stock, etc., and such termsare used interchangeably herein. A conventional cup design orconfiguration incorporating a relatively thin sheet material may notprovide the degree of strength and/or stability that is desired.

[0007] Such packaging also presents other problems. For example, thepackage may typically be filled with product at an elevated temperature.The elevated temperature may result from preparation of the productand/or from sterilization. In any event, the heated product maytemporarily reduce the rigidity or strength of the package material(such as a thermoplastic sheet material), and the package material maytend to soften, and then deform or stretch under the weight of theproduct deposited within the package. This may cause the bottom of thepackage to bulge convexly (i.e., downwardly or outwardly). When thepackage ultimately cools, the convex shape at the bottom of the packagemay remain, thereby creating a somewhat unstable support base for thepackage.

[0008] Such deformed package bottoms are sometimes referred to as“rocker bottoms.” A package with such a “rocker bottom” may tend to moreeasily tip over rather than sit flat on a table top or other flat,horizontal surface. Consequently, it would be desirable to provide animproved, low-cost package that can be processed at high speed and that,when filled with product at an elevated temperature, will have notendency, or only a minimal tendency, to develop a “rocker bottom” orother undesirable deformation.

[0009] Packages are typically subjected to external loads duringmanufacturing, distribution, storage, and use. For example, packages maybe stacked one on top of the other. Hermetically sealed packagesfabricated from thin sheet stock or film typically do not exhibitparticularly high resistance to stacking loads. Accordingly, it would bedesirable to provide a package of that type having increased compressionstrength so as to accommodate stacking loads without crushing a corneror other portion of the package.

[0010] Such a stronger package should not, however, require excessivelythick materials. Rather, such an improved package should accommodatefabrication from relatively thin sheet stock so as to permit the overallmanufacturing cost to be kept low and consistent with the desirabilityof providing a one-time use, disposable package.

[0011] Some products which are contained within hermetically sealedpackages may be deleteriously affected by certain packaging materials.For example, some packaging materials may permit an undesirable amountof ambient atmospheric substances (e.g., oxygen, water vapor, etc.) tomigrate through the package into the product contained therein. This maybe a significant problem for packaged products which are intended tohave long shelf lives. Accordingly, it would be beneficial to provide animproved sheet material for use in forming a package or portion thereof(e.g., the cup portion of a package) which would have the desiredbarrier properties relative to the ambient atmosphere during long-termstorage. Preferably, such an improved packaging sheet material shouldalso be thin enough to accommodate high-speed, low-cost manufacturing ofa disposable package.

[0012] Such an improved sheet material should also provide improvedcolumn strength, scratch resistance, impact strength, and superioraesthetic appearance.

[0013] Such an improved sheet material should also desirably accommodateits formation into a package body, container, or cup which is suitablefor being heat-sealed with a film lid. Further, the package shouldpreferably have a strong, hermetic, heat seal between the lid and cupwhich can be created with high-speed manufacturing techniques and whichpermits the lid to be easily removed by the user when the user desiresto open the package. Further, such an improved heat seal of the lid tothe cup should accommodate the optional incorporation of a lift-up tabor pull-up tab in the lid if desired,

[0014] Preferably, the improved heat seal between the package lid andpackage cup should also accommodate manufacturing proccessing whereinrows of cups and lids are heat-sealed together from a continuous web oflid material and a continuous web of cup material. The heat seal shouldaccommodate subsequent punching or separation of the individual, sealedpackages from the two continuous webs with the resulting, individualpackages having a few or no rough edges or stringy, “hair-like” strands,etc., around the periphery. In this respect, the improved package bodyor cup material, as well as the lid material, should accommodate thesevering of the individual packages from the continuous webs of materialin a way which will minimize, if not substantially eliminate, roughedges or hair-like filaments and strands of material about the peripheryof the package. This is especially important where the packaging usedfor a liquid food product which is intended to be drunk directly fromthe package cup after removing the package lid. In such applications, itis most desirable to provide a drinking edge which is clean and smooth.Some types of conventional package cups and hermetically sealed lids arefabricated, respectively, from a moving web of cup material and anoverlying moving web of lid material which has a composition thatdiffers from the composition of the cup material. The cup material istypically a type of thermoplastic which can be readily punched out ofthe web and which has a sufficient thickness and stiffness toaccommodate the punching of the package in a way that leaves arelatively smooth, non-stringy periphery. While such packages generallyfunction satisfactorily, it would be desirable to provide an improvedpackage design that could accommodate manufacture of the package cupportion from a thinner web of material and/or from other materials whichare difficult to smoothly punch, such as polypropylene. The use of theseother materials, such as polypropylene, for example, can provideimproved, or more desirable, properties with respect to the following:barrier characteristics, compatibility with various products, stabilityover an extended shelf life, resistance to degradation from ultravioletenergy, tolerance to thermal energy, and heat-seal formation withcertain types of lid materials.

[0015] Some types of packaging materials are more easily processed orformed into package bodies or cups than are other types of materials.With some types of materials, the manufacturing process must be verytightly controlled with respect to temperatures, formation forces, etc.,compared to using other types of packaging material which canaccommodate a greater latitude of processing parameters. However, insome applications certain types or materials which are difficult toprocess may nevertheless be preferred owing to improved packagingcharacteristics (e.g., strength). Thus, it would be desirable to providean improved method and apparatus for forming package bodies orcontainers from such types of materials, but at high speed and with areduced product reject rate.

[0016] In particular, it would be desirable to provide an improvedprocess and apparatus for heating the web of material so that it can bethermoformed into the package body or cup. Such an improved process andapparatus should tolerate minor misalignment of the thermoformingapparatus and web in both the machine web feeding direction and thetransverse or erode direction. The processing and for heating the webshould be effective to rapidly and effectively heat the material in acontrolled manner so that the final temperature is within a desiredrange to at each container-forming location across width of the web.

[0017] Additionally, the improved process and apparatus should permitthe high-speed formation of the body or cup portion of the package in away that results in the creation of the desired configuration andthickness of the wall as may be necessary to provide the desiredstrength and stability characteristics of the package. Such processesand apparatus should function at high speed, in aseptic environments andin a reliable manner with a minimum product reject rate.

[0018] The present invention provides an improved multi-ply sheet for acontainer and also provides a package comprising a container with ahermetically sealed lid having the above-discussed benefits andfeatures. Another aspect of the present invention includes an improvedmethod and apparatus for making the container and hermetically sealedpackage which can accommodate designs having the above-discussedbenefits and features.

SUMMARY OF THE INVENTION

[0019] According to one aspect of the present invention, a sealedpackage is provided with a container or cup having a body defining amouth and a flange around the mouth. A lid is disposed on the containeracross the mouth and flange. The flange has an annular, upset first beadof a heat-sealable thermoplastic material. The lid has an annular secondbead of a heat-sealable thermoplastic material adjacent the first bead.The first and second beads are sealed together with a first heat sealcomprising a resolidification of a melted interface portion of the firstand second beads.

[0020] Preferably, the lid and container flange are also attached withanother heat seal between an annular upset, third bead on the flange andan annular fourth bead on the confronting lid. In the preferredembodiment, the lid material is deformed into a recess in the containerflange between the two, annular heat seals. Preferably the lid andcontainer flange are also lightly bonded together between the outermostannular heat seal and the peripheral edge or the flange.

[0021] According to another aspect of the invention, a container/lidheat sealing tool is provided with an improved design. The tool includesa flat, inner annular ring, (2) an annular relief step, and (3) anintermediate annular groove between the ring and relief step. The ringprojects further than the relief step.

[0022] According to another aspect of the invention, a method isprovided for sealing a lid to a container. The method includes the stepof forming a first web of material into a container having a bodydefining a mouth and having a flange around the mouth. The flange has aninterior side with at least layer of heat-sealable thermoplasticmaterial and has an oppositely facing exterior side. The method alsoincludes the step of at least partially filling the container body witha product. According to the method, a second web of material is disposedacross the container body mouth and adjacent flange. The second web hasan exterior side facing away from the container and has an oppositelyfacing interior side. The second web has at least a layer of a heatuseable thermoplastic material on the interior side facing the layer ofheat-sealable thermoplastic material on the container flange.

[0023] The method further includes the step of forcing the second weband container flange together with a tool contacting the exterior sideof the second web and with an anvil contacting the exterior side of theflange so as to press the light-sealable thermoplastic polymer layerstogether. The tool has a flat, inner, annular ring, an intermediateannular groove, and a flat, outer annular relief step. The inner ringprojects further toward the body flange than does the relief step. Thedeepest part of the groove is further from the body flange than the ringand the step.

[0024] The method further includes the step of heating the heat-sealablepolymer layers so that an interface portion of the layers is in a meltedcondition at least for some period of time where they are pressedtogether. Portions of heat-sealable polymer layers may be heated andsoftened prior to the first and second webs being pressed together.However, in the preferred embodiment, the tool is at an elevatedtemperature as it contacts the exterior side of the second web andpresses the second web against the body container flange defined by thefirst web. At least a portion of each heat-sealable polymer layer ofeach web melts while the two webs are pressed together.

[0025] Subsequently, the tool is withdrawn from contacting the secondweb, and the melted interface portion is permitted to cool andresolidify to form a heat seal.

[0026] According to another aspect of the present invention, a muliplyweb or sheet is provided for being thermoformed into a cup, container,or the like. The sheet comprises five layers of materials which areco-extruded together to form a five-ply sheet. The five-ply sheetconsists of first, second, third, fourth, and fifth layers. In thepreferred embodiment, the sheet consists of only the five layers and isdevoid of a regrind layer.

[0027] The sheet first layer is adapted to function as the exterior sideof the package and preferably comprises polypropylene. The second layerfunctions as an adhesive joining the first and third layers. The thirdlayer functions as an oxygen barrier and preferably comprises ethylenevinyl alcohol. The fourth layer functions as an adhesive joining thethird and fourth layers. The fifth layer is adapted for functioning asthe interior side of the package and preferably comprises polypropylene.

[0028] Preferably, the sheet has a thickness in the range from about72.50 mils to about 95.50 mils. The first and fifth layers eachpreferably have a thickness in the range from about 33.75 mils to about43.75 mils. Each adhesive layer (i.e., second and fourth layers)preferably has a thickness in the range from about 1.50 mils to about2.50 mils. The third layer, which functions as an oxygen barrier,preferably has a thickness in He range from about 2.00 mils to about3.00 mils.

[0029] Another aspect of the present invention includes an apparatus forheating a web of sheet material prior to thermoforming the material intoa cup, container, or similar package component having a generallycircular, transverse cross section. The apparatus comprises at least oneheating plate. The apparatus further includes a pad associated with theheating plate for being conductively heated by the heating plate. Thepad has an oval configuration with a minor axis larger than the diameterof the largest transverse dimension of the package component portionwhich is to be thermoformed.

[0030] According to another aspect of the present invention, a method isprovided for heating a web of material prior to forming the materialinto a cup, container, or similar package component having a generallycircular cross section. The method comprises the steps of advancing theweb along a processing pack through a heating station having pads forcontacting the web where each pad has an oval configuration with a minoraxis larger than the diameter of the largest transverse dimension of thepackage component portion to be thermoformed. The method furtherincludes the step of effecting contact between the web and pads in theheating station. The method further includes heating the pads to conductheat into the web and then separating the web and pads.

[0031] Yet another aspect of the invention includes an apparatus forheating a web of sheet material in a controlled manner prior toformation of the material into a package component such as a cup,container, or the like. The apparatus defines a web processing pathalong which a web of the sheet material is conveyed. A plurality ofheating plates are provided adjacent the web processing path. Eachheating plate has one or more contact surfaces for contacting a side ofthe web so as to heat one or more portions of the web by conduction. Afirst set of heating plates is provided with the plates arranged inpairs spaced along the path, with each pair extending across the path. Asecond set of heating plates is located relative to the first set ofheating plates at a downstream location along the web processing path.The plates in the second set are arranged in groups of three heatingplates spaced along the path, with each group of three heating platesextending across the processing path. A third set of heating plates islocated relative to the second set of heating plates at a downstreamlocation along the web processing path. The plates in the third set arearranged in at least one group along the processing path. The heatingplates in each group in the third set are arranged in pairs extendingacross the processing path. The number of pairs of heating plates in thethird set of heating plates is less than the number of pairs of heatingplates in the first set of heating plates.

[0032] Another aspect of the invention includes a forming plug for usein thermoforming a container in a form, fill, and seal process. In thisprocess, the plug is urged against a heated web of polymeric material tostretch a portion of said web within a die cavity where air pressureforces the web portion off the plug and against the walls of the dipcavity go as to form at least a portion of the container.

[0033] The plug body portion defines a longitudinal axis. The bodyportion has a lower, cylindrical sidewall surface and a distal end. Thedistal end defines a peripheral, frustoconical surface extendinginwardly from the sidewall surface.

[0034] The present invention also includes a method for forming a cup,container, or the like, in a form, fill, and seal process with theabove-described plug. The method comprises the step of providing atensioned web of thermoplastic material. According to the method, theforming plug is moved into the web of material while tension ismaintained on the material. A portion of the material is stretchedthinner and conforms to a portion of the shape of the plug frustoconicalexterior surface. This locates the web portion within a die cavity wherethe web portion can be forced by compressed air off of the plug andagainst the interior surface of the die cavity which has a configurationconforming to the exterior surface of a portion of the container.

[0035] Another aspect of the present invention relates to a containerwhich is formed from a polymeric sheet material. The container comprisesa unitary structure of the sheet material which hag a peripheral flangedefining an opening, a downwardly and inwardly tapering hollow bodydefined around a longitudinal axes by a generally frustoconical, annularsidewall extending from the flange, and a bottom defined by an annularbase which extends from a lower end of the body sidewall and which isadapted to engage a flat support surface along a generally circular lineof contact, an annular, first end wall extending from the annular,curved, peripheral base and toward the opening, an annular, second endwall located closer to the opening than the first end wall and extendingaway from the first end wall both inwardly and toward the opening, and(4) a central, third end wall located closer to the opening than thesecond end wall and extending from the second end wall.

[0036] According to another aspect of the invention, a container isformed from a sheet material a a unitary structure having a peripheralflange defining an opening. The structure has a downwardly and inwardlytapering hollow body defined around a longitudinal axis by a generallyfrustoconical, annular sidewall extending from the flange. The structurehas a bottom which includes an annular, curved, peripheral baseextending from the lower end of the body sidewall. The sidewallincreases in thickness with increasing distance from the opening.

[0037] According to yet another aspect of the present invention, acontainer is formed from a sheet material and comprises a unitarystructure having a peripheral flange defining an opening. The structureincludes a downwardly and inwardly tapering hollow body defined around alongitudinal axis by a sidewall extending from the flange. The structurehas a bottom defined by an annular base extending from the lower end ofthe body sidewall and an end wall structure that extends radiallyinwardly from the peripheral base and that is located closer to theopening than is the peripheral base.

[0038] The present invention also contemplates a method for punching asealed package from first and second webs of material. The packageincludes a container that is formed from the first web and that has abody defining a mouth and has a surrounding flange unitary with theremainder of the first web. The lid is to be severed from a second webextending over the container mouth and flange when the container flangeis severed from the first web. The lid and container flange are attachedadjacent the periphery of the flange with an annular bond which alsoextends radially outwardly on the sheet beyond the flange. The methodcomprises the steps of providing a die that has an aperture forreceiving the container body and that has a bearing surface which isaligned to bear against at least an annular portion of the first webadjacent the annular bond radially outwardly of the container body andflange.

[0039] The method includes disposing the punch adjacent the second web.The punch has a peripheral cutting edge defining an acute angle. Theradially outermost portion of the cutting edge has a diameter less thanthe diameter of the die aperture in which the container body isdisposed.

[0040] The method includes effecting relative movement between the dieand punch in a direction generally perpendicular to the plane of thewebs so as to cut through the webs at the annular bond and thereby severan annular inner portion of the bond from an annular outer portion ofthe bond at the edge of the flange.

[0041] According to yet another aspect of the invention, a method isprovided for punching from first and second webs of materials a packagethat includes a container in the first web, the container having a bodydefining a mouth and having an radially outwardly extending annularflange around the mouth, the package further having a lid in the secondweb of material that extends across the mouth of the container, the lidbeing sealed to the first web. The method includes the step of providinga die having a circular aperture for receiving the container body andhaving a support surface for supporting or bearing against the containerflange. The method further includes the step of effecting relativemovement between the die and punch in a direction generallyperpendicular to the plane of the webs. The punch has an annular cuttingedge defining an acute included angle. The radially outermost part ofthe annular cutting edge has a diameter less than the diameter of thedie aperture whereby an annular clearance is provided between theannular cutting edge and the die as the punch cutting edge and dieassume relative positions wherein the punch cutting edge is within thedie aperature upon severing the sealed lid and container from theremaining peripheral portions of the webs.

[0042] Yet another aspect of the present invention includes an apparatusfor punching a sealed package from first and second webs of materialwherein the package includes a container formed from the first web, thecontainer having a body defining a mouth and a flange surrounding themouth, the package further including a lid formed from the second webextending the container mouth and flange, wherein the webs are attachedwith an annular bond extending radially outwardly beyond the flange todefine an annular inner portion of the bond on the flange and to definean annular outer portion of the bond beyond the flange.

[0043] The apparatus also includes a die having an aperture forreceiving the container body. The aperture has a diameter larger thanthe outer diameter of the flange and has a bearing surface which isaligned to bear against at least an annular portion of the first webradially outwardly of the flange.

[0044] The apparatus includes a punch for engaging the second web. Thepunch has a cylindrical outer surface and an intersecting frustoconicalinner surface which together define an acute angle peripheral cuttingedge having an outer diameter which is substantially equal to the outerdiameter of the flange and less than the diameter of the die aperture soas to define an annular clearance. The apparatus also includes actuationmeans for effecting relative movement between the die and punch in adirection generally perpendicular to the plane of the webs to cutthrough the webs at the annular bond between the inner and outerportions of the bond and thereby sever the package from the webs alongthe outer diameter of the flange.

[0045] Numerous other advantages and features of the present inventionwill become readily apparent from the following detailed description ofthe invention, from the claims, and from the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In the accompanying drawings that form part of the specification,and in which like numerals are employed to designate like partsthroughout the same,

[0047]FIG. 1 is a perspective view of a package embodying variousfeatures of the present invention, and FIG. 1 shows an optional cover inan exploded view above the package;

[0048]FIG. 2 is a fragmentary, cross-sectional view of a sheet ofmaterial that can be used to form the container which is part of thepackage shown in FIG. 1;

[0049]FIG. 3 is a cross-sectional view of the container portion of thepackage shown in FIG. 1;

[0050] FIG. it is a fragmentary, perspective view of sheet materialundergoing a forming step in accordance with the present invention;

[0051]FIG. 5 is a greatly enlarged, fragmentary, cross-sectional viewtaken generally along the plane five-five in FIG. 1;

[0052]FIG. 6 is a greatly enlarged, fragmentary, cross-sectional viewtaken generally along the plane 6-6 in FIG. 1;

[0053]FIG. 7 is a simplified, perspective view of a conventional machinewhich can be modified to incorporate features of the present invention;

[0054]FIG. 8 is a cross-sectional view of a portion of the machine inFIG. 7 which can incorporate the modified heating plates of the presentinvention;

[0055]FIG. 9 is a schematic illustration of the arrangement of theheating plates according to the principles of the present invention;

[0056]FIG. 9A is a fragmentary, perspective view of a modified heatingplate of the present invention;

[0057]FIG. 10 is a fragmentary, plan view taken generally along theplane 10-10 in FIG. 9A;

[0058]FIG. 11 is a bottom plan view of a container-forming plugembodying features of the present intention

[0059]FIG. 12 is a cross-sectional view taken generally along the plane12-12 in FIG. 11;

[0060]FIG. 13 is a bottom plan view of a heat sealing tool embodyingfeatures of the present invention;

[0061]FIG. 14 is a greatly enlarged, fragmentary, cross-sectional viewtaken generally along the plane 14-14 in FIG. 13, and a lid sheet andcontainer sheet are shown disposed below the tool;

[0062]FIG. 15 is a greatly enlarged, fragmentary, cross-sectional viewtaken generally along the plane 15-15 in FIG. 13;

[0063]FIG. 16 is a fragmentary perspective view of the top of thepackage shown in FIG. 1: FIG. 17 is a view similar to FIG. 16, but FIG.17 shows the package tab being grasped to open the lid;

[0064]FIG. 18 is a fragmentary perspective view of a portion of thedie-cutting station of the machine shown in FIG. 7 and illustrating themodified punch and die sets incorporating features of the presentinvention; and

[0065]FIG. 19 is a fragmentary, cross-sectional view of one of the punchand die sets shown in FIG. 18.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0066] While the various aspects of this invention are susceptible ofembodiment in many different forms, this specification and theaccompanying drawings disclose only one specific form of each aspect ofthe invention as an example of the invention. Each aspect of theinvention is not intended to be limited to the particular embodiment sodescribed, however. The scope of the invention is pointed out in theappended claims.

[0067] For ease of description, the articles and apparatus of thisinvention are described in an upright operating position as depicted inthe accompanying figures and terms such as upper, lower, horizontal,etc., are used with reference to this position. It will be understood,however, that the article and apparatus of this invention may be dispod,stored, and/or used, at least temporarily, in an orientation other thanthat described.

[0068] Figures illustrating the apparatus and method of the inventionshow some mechanical elements that are known and that will be recognizedby one skilled in the art. The detailed descriptions of such knownelements are not necessary to an understanding of the invention, andaccordingly, such known elements are herein described only to the degreenecessary to facilitate an understanding of the novel features of thepresent invention.

The Package

[0069]FIG. 1 illustrates a package 20 which incorporates various aspectsof the present invention. The package 20 may be employed for packaging afood product or medical product by means of an aseptic filling processfollowing sterilization of the product. Such a process does not requireterminal sterilization, thereby eliminating, or at least substantiallyminimizing, the possibility of changes in, or damage to, the productand/or package that might occur during terminal sterilization.

[0070] Various features of the package 20 are designed to accommodate(1) formation of the package components, (2) aseptic filling of apackage container with a product, and (3) closure and sealing of thepackage components. Further, the package 20 employs features of thepresent invention which accommodate high speed, high volume productionof the completed package with automatic machinery.

[0071] The improved package design features also permit the use ofrelatively thin sheet material for the package components whileproviding the desired strength, particularly with respect to resistanceto bulging and crushing. The package also has improved scratchresistance, high impact strength, and a desirable aesthetic appearance.

[0072] The preferred embodiment of the package 20 illustrated, althoughmanufactured from relatively thin sheet material, provides variousdesired properties relative to long-term product storage. The preferredmaterials employed in the package are compatible with a wide variety ofproducts, are stable over an extended shelf life, resist degradationfrom ultraviolet energy are tolerant of thermal energy and providesuperior heat-seal formation characteristics with respect to the packageclosure seal.

The Sheet from Which the Package Container is Formed

[0073] The package 20 includes a cup or container and a sealed lid 40which has an integral pull tab or lift tab 42. The terms “cup” and“container” are used herein interchangeably to refer to the structurewhich is formed with one closed end and one open end that can besubsequently closed or sealed with the lid 40. An optional snap-fitovercap 50 may be provided for snap-fit engagement with the containerover the lid 40.

[0074] According to one aspect of the invention, the cup or container 30is preferably thermoformed from a novel, multi-ply web or sheet 90 whichis shown in cross section in FIG. 2. The sheet consists of five layersof material co-extruded together to form a five-ply sheet consisting ofa first layer 61, a second layer 62, a third layer 63, a fourth layer64, and a fifth layer 65.

[0075] The first layer 61 is adapted for functioning as the exteriorside of the package container 30 and preferably comprises polypropylene.In the preferred embodiment, the polypropylene is grade 7292N sold underthe brand name ESCORENE by Exxon Chemical Company, P. O. Box 3272,Houston, Tex. 77253-3272.

[0076] Preferably, the polypropylene used for the first layer 61 isproduced with a controlled cooling of the nucleated polypropylene tomaximize crystallinity and orientation so as to increase the flexuralmodulus of the material. Preferably, the polypropylene has an impactblock copolymer polypropylene structure which balances good molecularflexibility (which provides improved impact strength) with relativestiffness (which provides increased creep resistance).

[0077] The polypropylene first layer 61 also preferably includes anominal 4% rutile grade titanium dioxide to provide a light barrier andto enhance the appearance of the package such that the polypropylenefirst layer 61 has what lay people regard as, or associate with, atechnical or medical appearance.

[0078] The second layer 62 functions as an adhesive joining the firstlayer 61 and third layer 63. Preferably, the adhesive is grade QF 551Asold under the trademark ADMER by Mitsui Petrochemicals (America), Ltd.,250 Park Avenue, Suite 950, New York, N.Y. 10177-0056.

[0079] The third layer functions as an oxygen barrier and comprisesethylene vinyl alcohol. Preferably, the ethylene vinyl alcohol is gradeJ102 sold under the trademark EVAL by EVAL Company of America, 1001Warrenville Road, Suite 201, Lisle, Ill. 60632-1359. This productincludes 32% ethylene vinyl alcohol with a nominal 4% rutile gradetitanium dioxide to provide improved barrier properties with respect tomoisture and light as well as oxygen.

[0080] The fourth layer 64 functions as an adhesive joining the thirdlayer 63 and fifth layer 65. The adhesive fourth layer 64 preferably hasthe game composition as the adhesive second layer 62 described above.

[0081] The fifth layer 65 is adapted for functioning as the interiorside of the package container 30. The fifth layer 65 preferablycomprises polypropylene of the same type as in the first layer 61described above.

[0082] In the preferred embodiment, the layers 61-65 in the web or sheet90 each have a nominal design thickness and design range thickness asset forth in Table I. TABLE 1 THICKNESS OF CONTAINER SHEET LAYERS DesignThickness Nominal Range Sheet Layer Dimension Thickness ThicknessDesignation Designation (Mils) (Mils) 61 A 38.75 33.75-43.75 62 B 2.001.50-2.50 63 C 2.50 2.00-3.00 64 D 2.00 1.50-2.50 65 E 38.75 33.75-43.75

[0083] When the container is manufactured according to a preferredprocess described hereinafter, the multi-ply sheet 90 is provided withonly the five above-described layers and is devoid of any regrind layer.The sheet 90 preferably has a total thickness, prior to formation into acontainer 30, ranging between about 72.50 mils and about 95.50 mils.

[0084] The structure, composition, and thickness of the sheet 90 providea superior thermoforming capability and long-term dimensional stability.The multi-ply sheet 90 has a flexural modulus of approximately 160,000pounds per square inch.

The Container

[0085] When the sheet 90 is formed into the container (by processesdescribed in detail hereinafter), the container 30 is strong and hassuperior compression strength. The container is also sufficientlyresistant to normal hand squeezing so as to accommodate use of thecontainer for holding typical consumer food products. The container 30can also withstand significant impact which might be experienced if itis dropped or bumped during routine shipping and handling.

[0086] When the container 30 is formed from the multi-ply sheet 90 andhas the configuration and dimensions described in detail hereinafter,the container provides good barrier protection with respect to moisture,oxygen, and light. Specifically, moisture transfer through the container30 (as measured with the container 30 attached to a test fixture inplace of the lid 40) is less than or equal to 0.1 gram per day. Theoxygen transfer through the container is less than or equal to 0.01cubic centimeters per day. The light transmission through any portion ofthe wall of the container is less than or equal to 0.1% for a test lightwave length of 450 nanometers.

[0087] According to one aspect Of the invention, the cup or container 30is provided with a unique configuration which increases the capabilityof the container to withstand squeezing and crushing and which canaccommodate filling with a product at an elevated temperature withoutsignificant deformation.

[0088]FIG. 3 illustrates the cross-sectional configuration of the cupcontainer 30. The container is preferably formed from theabove-described, multi-ply sheet 90. For ease of illustration, the fivelayers 61-65 of the multi-ply sheet 90 which define the container wallare not individually shown in FIG. 3. Rather, the container wall isillustrated simply as one layer. However, it is to be understood that inthe preferred embodiment, the container wall comprises the five-layersheet 90 described above.

[0089] With reference to FIG. 3, it can be seen that the container is aunitary structure having a peripheral flange 70 defining an opening 72.The container includes a downwardly and inwardly tapering hollow bodydefined around a longitudinal axis 73 by a generally annular sidewall 74extending from the inner edge of the flange 70.

[0090] The container 30 has a bottom end 76. The bottom 76 is defined,in part, by an annular, curved, peripheral base 78 extending from alower end of the body sidewall 74. The bottom end 76 is adapted toengage a flat support surface along a generally circular line ofcontact. The base 78 also including an annular first end wall 80extending from the annular, curve, peripheral base 78 both inwardly andupwardly toward the opening of the container mouth 72.

[0091] The container bottom end 76 also includes an annular, second endwall 82 which is located closer to the opening or mouth 72 than is thefirst end wall 80. The annular, second end wall 82 extends from thefirst wall 80 both inwardly and upwardly toward the container mouth 72.

[0092] The container bottom end 76 also includes a central, third endwall 84 located closer to the container mouth 72 than is the second endwall 82. The third end wall 84 extends from the second end wall 82 andhas a generally circular, disc-like configuration.

[0093] In the preferred embodiment, the first end wall 80 defines asubstantially frustoconical exterior surface defining an angle of about79° relative to the longitudinal axis.

[0094] Preferably, the thickness of the container sidewall 74 increaseswith increasing distance from the flange 70 toward the bottom end 76.The thickness of the sidewall 74 at various locations along its heightis listed below in TABLE 2 with reference to the FIG. 3 thicknessdesignations AA, RD, CC, DD, EE, FF, and GG. Other dimensions of thecontainer 30, including angular orientations of portions of thecontainer are also set forth in TABLE 2. TABLE 2 Container DimensionNominal Dimension Design Designation Dimension Range or Minimum A  0.00in. — B  0.50 in. — C  1.00 in. — D  7.50 in. — E  2.00 in. — F  2.50in. — G  3.25 in. — H   100 mm. — I  3.2E 1.8E-3.2E J   76 mm. — K   67mm. — L   14 mm. — M 46.26 mm. — N 55.82 mm. — O  0.5 mm. — P  0.5 mm. —Q   45E — R  0.5 mm. — S  4.5 mm. — T  0.3 mm. — U  5.0 mm. 3.0 mm.-5.0mm. AA 0.010 in. 0.008 in. minimum BB 0.010 in. 0.008 in. minimum CC0.010 in. 0.008 in. minimum DD 0.011 in. 0.008 in. minimum EE 0.012 in.0.008 in. minimum FF 0.014 in. 0.010 in. minimum GG 0.020 in. 0.015 in.minimum HH 0.016 in. 0.012 in. minimum

[0095] The preferred embodiment of the container incorporating thedimensions set forth in FIG. 2 can withstand top loading forces of amagnitude normally encountered when the containers are stacked in salesdisplays as well as when the containers are stacked duringmanufacturing, packing, and distribution. The configuration of thecontainer base 78 and bottom corner of the container 30 provides acompression strength which is sufficient to prevent corner crushingunder loads that are normally encountered. The steep angle of thecontainer wall 74, and the change in thickness of the wall 74 relativeto the wall height, contribute to providing compression strengthsufficient to accommodate compression loads that are normallyencountered. However, the angle of the wall 74 is sufficient tofacilitate removal of the container 30 from an exterior forming die(during a forming process described hereinafter in detail).

[0096] The configuration of the container bottom end 76 concentrates thecontainer material in those regions where it is desired to haveadditional rigidity so as to withstand the weight load of a productdispensed into the container, especially while the container is stillwarm from the thermoforming process preferably used to make thecontainer. The container bottom end configuration resists the tendencyof the container material to deform under a load, especially when thematerial is warm, thereby preventing the formation of an outwardlyconvex deformation or bulge (“rocker bottom”) which could make thecontainer base or bottom unstable.

The Package Lid

[0097] The above-described, improved container is particularlywell-suited for use in the sealed package 20 which includes the lid 40.The lid 40 is heat-sealed in a unique manner to the top of the containerflange 70. The lid 40 may be made from a suitable conventional orspecial material that can be heat-sealed, at least in a region on thecontainer flange 70. In a preferred embodiment, the lid material is amulti-ply material having a conventional layered or laminated structure.A presently preferred commercial lid material is sold under thedesignation Safe-Gard™ Y-523 Top Tabbed Induction Innerseal by 3MCompany, St. Paul, Minn. 55144-1000, U.S.A.

[0098] The Safe-Gard™ material for the lid 40 is preferably provided inthe form of a wide web or sheet in a roll. FIG. 4 illustrates such awide sheet 92 of the lid material shown disposed in a flat, horizontalorientation over a plurality of containers formed in, and stillconnected to the above described web or sheet 90. The areas of the lidsheet 29 which will each ultimately become separate lids 40 on eachcontainer 30 are shown in phantom in FIG. 4 and are designated thereinby the reference numeral 40′.

[0099] One or more top plies or layers of the lid sheet 92 are notlaminated to the underlying plies in spaced-apart, strip regions 94(FIG. 4). The parallel, spaced-apart, strip regions 94 are connected tothe rest of the sheet 92 along, and beyond, lateral margins 96. Eachstrip region 94 is not connected to the underlying portion of the sheet92 between its two lateral margins 96.

[0100] When the lid sheet 92 is disposed over the tops of the containers30 prior to sealing the sheet 92 to the containers, preferably,substantially one-half of the top of each container 30 extends under astrip region 94, and the other half of the container extends under theadjacent, fully laminated plies of the lid sheet 92. After the sheet 92is sealed to the tops of the containers (by a process described indetail hereinafter), the individual lid regions 40′ are punched out fromthe remaining portions of the lid sheet 92 along with the individualcontainers 30 which at the same time are separated from the remainingportion of the container sheet steel 90 by the same punching process.The punching process creates the hinged, substantially semi-circular tab42 (FIG. 1) over one-half of the lid 40, and the tab 42 is hinged to thelid 40 along one of the lateral margins 96 of the lid sheet strip region94 (FIG. 4).

[0101] The multi-ply structure of each individual lid 40 is illustratedin FIG. 5. When the above-identified Safe-Gard™ Y-523 material is usedfor the lid 40, the lid 40 has a top layer 101, a second layer 102, athird layer 102, a fourth layer 104, and a fifth layer 105. An extralayer 106 is also provided on the underside of the tab 42. The extralayer 106 is not attached to the underlying layer 103. The semi-circulartab 42 is attached to the lid 40 along its diameter (across the diameterof the container 30) at the lateral margin 96 (which is part of one ofthe same lateral margins 96 of one of the strip regions 94 in the lidsheet 92 (FIG. 4).

[0102] The layers 101-106 of the above-identified Safe-Gard™ Y-523 lidcompositions and thicknesses as set forth in TABLE 3 below. TABLE 3 LidLayer Lid Layer Designation Lid Layer Nominal In FIG. 3 CompositionThickness 101 Polyester Film  0.0008 in. 102 Co-polymer Adhesive  0.0032in. 103 Aluminum Foil  0.0010 in. 104 Polyester Film 0.00056 in. 105Heat Sealable Film  0.0012 in. 106 Polyester Film (present only on 0.0015 in. underside of tab 42 and adhered to polyester top film layer101)

[0103] The heat-sealable film layer 105 may be a heat-sealable film soldin the U.S.A. under the designation PEELEX by Lawson Mardon.

[0104] The overall thickness of the multi-ply lid 40, in the preferredembodiment, is about 0.0072 inch, plus/minus 0.0005 inch.

The Package Seal

[0105] The lid 40 is sealed to the container flange 70 in a processperformed by an apparatus described in detail hereinafter. The sealformed between the lid 40 and the container flange 70 has a uniqueconfiguration which provides improved attachment and sealingcharacteristics.

[0106]FIG. 6 illustrates the attachment of the lid 40 to the containerflange 70 in the half of the lid that is not under the loose tab 42.FIG. 6 is a somewhat simplified illustration, and portions of FIG. 6 aredepicted as being disproportionately larger or smaller than otherportions for clarity of illustration.

[0107] A relatively strong annular bond is formed at a first heat seal121. The heat seal 121 comprises a resolidification of a meltedinterface portion of the lid 40 and flange 70.

[0108] In particular, the flange 70 has an annular, upset, first bead131 which projects slightly above the rest of the upper surface of theflange 70. The annular bead 131 is formed during the lid heat sealingprocess described in detail hereinafter.

[0109] Adjacent the first bead 131, and radially outwardly thereof, is asecond bead 132 which is formed from fusion of the lid layer 105 and lidlayer 104. The layers 105 and 104 which initially extend across theentire bottom of the lid sheet material are deformed and squeezed duringthe heat sealing process (described in detail hereinafter) such thatsome of the material of the layers 105 and 104 radially inwardly of theflange bead 131 is displaced laterally and forming the bead 122.

[0110] The beads 131 and 132 are heat sealed together at the heat seal121. The heat seal 121 comprises a resolidification of a meltedinterface portion of the lid second bead 132 and the flange first bead131.

[0111] An annular, second heat seal 122 is formed inwardly of the firstheat seal 121. The second heat seal 122 is defined between an annular,upset third bead 133 on the flange 70 and an annular fourth bead 134 inthe lid 40. The lid fourth bead 134 is formed during the heat sealingprocess described hereinafter wherein some of the material of the lidlayers 105 and 104 is squeezed and displaced radially inwardly. Duringthe heat sealing process, the annular, upset third bead 133 is formed onthe flange 70. The second heat seal 122 comprises resolidification of amelted interface portion of the flange third bead 133 and lid fourthbead 134.

[0112] When the heat seals 121 and 122 are formed by the processdescribed in detail hereinafter, the displacement of the material fromthe bottom layers 105 and 104 to form the lid beads 132 and 134 resultsin the elimination, or at least substantial reduction, of the layers 105and 104 from the annular region 138 which is defined between the two lidbeads 132 and 134. In the region 138, the foil layer 103 substantiallycontacts the container flange material but does not form a significantlystrong heat seal bond with the flange material. The region 138 isdefined by a recessed area in the lid material, and some of the lidmaterial is laterally deformed outwardly to form the upset beads 131 and133 at the recess outer edge and recess inner edge, respectively.

[0113] The heat sealed inner beads 133 and 134 necessarily cause a bulgeor slight upward projection 140 at the top surface of the material ofthe lid 40. Similarly, the heat sealed outer beads 131 and 132 cause theupper surface of the material of the lid 40 to project slightlyoutwardly at 142.

[0114] Radially inwardly from the lid bead 134 there is little or nosignificant attachment of the lid 40 to the underlying flange 70. Thelid 40 in that region is thus free to be flexed slightly upwardly fromthe upper surface of the flange 70, depending upon the forces acting onthe lid 40 from either inside the container or outside the container anddepending upon the degree of tension existing in the lid 40 across thediameter of the inner seal 122.

[0115] The top surface of the lid 40 immediately adjacent, but radiallyinwardly of, the projection 140 is designated in FIG. 6 by the referencenumber 146. The height of the lid exterior surface at location 146 isequal to the thickness of the lid material where it contacts the surfaceof the container flange 70 just radially inwardly of the inner, annularseal 122. The surface of the lid 40 at the top of the projection 140 maybe a small distance A above the surface 146.

[0116] Outwardly of the projection 140, the lid material is recessedbelow the surface 146 by the amount indicated by the reference letter B.

[0117] The outer projection 142 at the top of the lid 40 may projectabove the surface 146 by a small amount indicated by the referenceletter C. Radially outwardly of the projection 142, the upper surface ofthe lid 40 may be slightly depressed by an amount designated with thereference letter D. However, there may be only a very slight depression,or no depression, of the outer portion of the lid so that D may be zeroor close to zero.

[0118] At the bottom surface of the lid 40 outwardly of the outer seal121, the lid 40 may b lightly attached or “tacked” by a heat bond to thetop surface of the container flange 70 as indicated by the region 150 inFIG. 6.

[0119]FIG. 6 illustrates the container flange 70 sealed to a portion ofthe half of the lid 40 which includes all five layers laminatedtogether. The other half of the lid 40, under the lift-off tab 42, wouldonly have the bottom three layers 103, 104, and 105 laminated togetherand sealed to the lid flange 70 (compare with FIG. 5). Because the lid40 is sealed to the container flange 70 with the tab 42 flat against theunderlying lid portion, the tab 42 also bears the heat seal imprint ofthe heat seal tool (described hereinafter in detail). However, after thesealed package is punched out of the lid sheet 92 and container sheet90, the lid tab 42 is free to pivot upwardly from the lid about the tabhinge 96.

[0120] The seal of the container flange 70 to the laminated three-layerhalf of the lid 40 under the tab 42 has a profile substantially similarto that illustrated in FIG. 6 except that the top two layers 101 and 102shown in FIG. 6 are in the hinged tab 42. The lid seal structureunderlying that tab 42 has the following configuration; (1) a recessedregion (similar to region 138 in FIG. 6), (2) flange beads (similar tobeads 131 and 133 in FIG. 6), (3) lid beads (similar to beads 132 and134 in FIG. 6), and (4) lid projections (similar to projections 140 and142 in FIG. 6). However, the overall thickness of the lid 40 in the areaunder the tab 42 is thinner by an amount equal to the thickness of thelayers 101 and 102.

[0121] To assist in opening the lid 40, the above-described lid sealstructure preferably has two small areas at the outer edge of the lidwhich differ slightly from the remaining annular portion of the sealstructure. These two areas are identified in FIG. 16 with dashed linesand are designated by reference number 151.

[0122] The two areas 151 are 180 degrees apart on the ends of the liddiameter hinge line 96 which connects the tab 42 to the lid 40. The twoareas 151 have a weaker bond or tacking attachment of the lid 40 to thecontainer flange 70 than exists around the remaining peripheral edgeportions beyond the two areas 151.

[0123] It will be recalled that the lid 40 was previously described asbeing only lightly bonded to the container flange 70 in the outermost,annular region 150 shown in FIG. 6. However, the two areas 151 in theannular region 150 represent an even weaker bond or no bond at all, Theareas 151 do not extend radially inwardly so far that they affect theouter, full heat seal 121 (FIG. 6).

[0124] The relatively weak bond (or bond-free) areas 151 facilitate theopening of the lid 40 when the tab 42 is pulled upwardly as shown inFIG. 16. Because the areas 151 at each peripheral end edge of the tabhinge connection 96 have no bond or a relatively weak bond between thelid 40 and container flange 70, the lid 40 can be initially pulled awaymore easily in the areas 151 compared to the remaining areas of theperiphery of the cup. FIG. 17 shows how the lid 40 is initially andpreferentially pulled away from the container flange 70 in a tent-likeconfiguration at one of the areas 151 when the tab 42 is pulledupwardly. This provides a means by which the opening of the lid 40 canbe readily started so that continued pulling on the tab 42 will thenopen the full heat seals 121 and 122 (FIG. 6) whereby the lid 40 becomescompletely detached.

[0125] The novel lid seal structure described above provides a number ofdesirable characteristics and advantages. The above-described heat sealbead structure, such as the heat seal 121 of the flange bead 131 to thelid bead 132 and/or the heat seal 122 of the flange bead 133 to the lidbead 134, provides a high-strength attachment and a highly effective,leak-tight seal which has a relatively high burst strength. Tho seals121 and 122 are less likely to fail when the package is subjected toimpacts and/or pressure gradients.

[0126] Further, it has been found that the above-described sealstructure is effective in preventing, or substantially minimizing,wrinkling of the lid material. In particular, after the lid sheetmaterial is heat-sealed to the containers, the lid material is permittedto cool. In some cases, there may be a tendency of the lid material tocontract and/or produce wrinkles across a portion of the lid. This mayresult in the formation of channels through the seal area which wouldfunction as leakage passages. The above-described new seal configurationof the present invention eliminates such wrinkles or at least minimizessuch wrinkles to the extent that leakage passages or channels do notdevelop in the seal.

[0127] It should also be noted that the width of the annular recess 138,along with the radially outwardly extending, lightly heat-bonded region150, provides a large area which is heated with the heat-sealing toolduring the heat-sealing process described hereinafter. The large, heatedarea permits sufficient heat to be added to the lid and flange materialsso that properly formed, strong heat seals are created with the desiredconfiguration.

[0128] It will also be appreciated that the novel heat sealconfiguration of the present invention, while providing a high-strength,hermetic seal, also permits the lid to be relatively easily removed bythe user when the user pulls on the tab 42.

[0129] The Completed Package

[0130] The above-described heat seal of the present invention whichbonds the lid 40 to the container 30 contributes to the strength of thecompleted package 20 so as to effectively contain and protect theproduct therein. The preferred embodiment of the package provides aminimum of 60 pounds compression strength as measured by a test basedupon ASTM D695. This is sufficient to withstand the postulated maximumcrushing load to which the package 20 might typically be subjectedduring distribution and handling.

[0131] The package 20, when fabricated from the above-describedpreferred materials, offers sufficient barrier protection with respectto moisture, oxygen, and light for many contemplated packagingapplications.

[0132] Further, the exterior surfaces of the package are relativelyresistant to tearing, scratching, abrasion, puncturing, etc.

[0133] Also, the exterior surfaces of the package exhibit, or can beprovided with, surface finishes and/or coatings which would provide apleasing aesthetic appearance or other special appearance.

METHOD AND APPARATUS FOR MAKING THE PACKAGE General Arrangement of theApparatus

[0134] Referring now to the drawings, the general arrangement andsequence of operation of an apparatus for making the package 20 can bebest understood with reference to FIG. 7. FIG. 7 illustrates a packagingmachine 157 that has certain components that can be modified and/orreplaced in accordance with the teachings of various aspects of thepresent invention to produce the above-described package 20. An exampleof a machine 167 is sold in the U.S.A. under the model designation TFA7033 by Robert Bosch Corporation, 121 Corporate Blvd., South Plainfield,N.J., U.S.A., 07080.

[0135] The machine 157 includes a spool support and feeding station 160.In the station 160, the container or cup sheet 90 is drawn from a spoolor roll 162. The cup sheet 90 is processed by the machine 157 so as tothermoform the cups 30, fill the formed cups 30, heat-seal the lid sheet92 to the cups 30, and then die-cut the sealed lid/cup package from thelid and cup sheets.

[0136] Typically, the machine 157 is operated to initially perform aseries of self-cleaning steps using a combination of hydrogen peroxide,sterile air, and/or steam to insure that a sterile environment ismaintained within the machine.

[0137] The cup or container sheet 90 is drawn from the feeding station160 through a hydrogen peroxide bath station 166 so as to sterilize thesheet 90.

[0138] The sheet 90 then passes into a sterile or aseptic zone in themachine which includes a heating station 170. The heating station 170comprises eight heating substations of equal width. The sheet 90 isincrementally advanced or indexed through the machine 157. During eachindexed advancement of the sheet 90, the sheet moves a distance equal tothe centerline spacing between adjacent heating substations.

[0139] In each heating substation, there are twenty-four areas of thesheet 90 which are heated by direct contact of both side surfaces of thesheet with twenty-four heating pads on each side surface as to raise thetemperature of each area of the sheet 90. The temperature of each of thetwenty-four areas of the sheet 90 increases as the sheet 90 isincrementally indexed through each of the eight heating substations.Each heating substation is designed to heat the twenty-four areas on thesheet 90 for accommodating subsequent thermoforming of twenty-fourcontainers simultaneously. The twenty-four areas on the sheet 90 in eachof the eight heating substations are contacted directly by twenty-fourtop surface heating pads and twenty-four bottom surface heating padsarranged in an array of six rows of pads across the width of the machine(“transverse direction”) and four pads in each row along the length ofthe machine (“machine direction”).

[0140] The heated sheet 90 leaves the heating station 170 and enters thethermoforming station 190. In the thermoforming station 180, the heatedsheet is deformed by twenty-four reciprocally moving plugs that forceportions of the heated sheet downwardly into corresponding die cavities.A short blast of sterile, compressed air is simultaneously injected overthe top surface of the sheet 90 to blow the sheet away from the plugsand against the die cavities to form the containers or cups. The formingplugs are reciprocally moved upwardly and way from the formedcontainers. The forming plugs are preferably water-cooled to preventoverheating.

[0141] The formed cups leave the thermoforming station 180 asprojections extending downwardly from the remaining flat portions of thesheet 90. The cups then enter the filling station 190. In the fillingstation 190, nozzles are lowered into each cup to deliver a sterilizedproduct into each cup. The product is typically a fluid, and can bedispensed from a large holding tank by means of a conventional slidewall piston filling mechanism or other known means for delivering afluid from a holding tank to a nozzle.

[0142] Lowering of the filling nozzles into each cup minimizes the dropheight of the product during filling which eliminates product splash andafter-drip. This also minimizes foaming and facilitates more effectivesealing of the lid to the cup owing to the elimination or minimizationof contamination on the cup flange sealing surface.

[0143] After the cups are filled, they are indexed with the sheet 90 tothe lid sealing station 200. Here the lid sheet 92 is sealed to thecups. The lid sheet 92 is drawn from a roll 210 rearwardly over the topof the sealing station 200 and then down through a hydrogen peroxidesterilizing bath in a lid sheet sterilizing station 220 prior to beingindexed through the sealing station 200 above the cups formed in thesheet 90.

[0144] The cups entering the sealing station 200 leave the precedingsterile zone of the machine through a discharge lock, and twenty-fourcups are simultaneously sealed to the overlying lid sheet 92 withtwenty-four individual heat seal tools in sealing station 200. Indexgroupers are used to prevent product spillage from the containersadvancing through the sealing station 200.

[0145] At the sealing station, the lid sheet 92 is sealed tightly to therim or flange of each cup. The sealed assembly is immediately cooled tominimize warpage.

[0146] The formed, filled, and sealed assembly is then indexed to adie-cutting or trim station 230. Twenty-four punch and die tool sets areoperated in the trim station 230 to separate the sealed cup and lidpackage from the remaining web portions of the lid sheet 92 andcontainer sheet 90. Typically, a motor control system is utilized tocontinually adjust the registration of the punch and die sets tocompensate for any variation due to sheet shrinkage during processing.

[0147] The die-cut remaining portion or matrix of the lid sheet 92 andcontainer sheet 90 is accumulated on a winder in a scrap dischargestation 240 where it is shopped into strips and discharged onto aconveyor belt for recycling.

[0148] The finished packages are transported to a secondary packagingarea by means of a walking beam transport system. This insures accurateindexing for any subsequent processing steps, such as boxing.

[0149] The machine of the present invention operates at about eighteenindexing cycles per minute where each indexing cycle is defined ascomprising the stationary dwell of the sheet at a station while thestation operates on the sheet plus the sheet advancement from onestation to the next.

[0150] The aspects of the present invention which involve modificationsto the machine are described in detail hereinafter. The conventionalmechanisms and elements of the machine which are not modified accordingto the present invention either are not described herein in detail orare described herein only in sufficient detail so as to afford anunderstanding of the relationship to the teachings of the presentinvention. The details of the design and operation of such unmodified,conventional elements of the machine 157 form no part of the presentinvention.

Improved Container Sheet Heating Process and Apparatus

[0151] The machine heating station 170 raises the temperature of groupsof twenty-four areas the container sheet 90 so that they may besubsequently formed into twenty-four container or cup bodies. Accordingto one aspect of the invention, some or the sheet contact heatingelements are arranged in specific configurations and groupings so as topermit improved control of the sheet temperature. According to anotheraspect of the invention, each container sheet contact-heating surfacehas a special configuration which accommodates potential misalignment ofthe sheet as it is indexed through the machine.

[0152] Specifically, as shown in FIG. 8, the heating station 170includes eight heating substations 271, 272, 273, 274, 275, 276, and278. The heating substations 271-278 each include upper and lowerheating plates for contacting the top and bottom surfaces, respectively,of the cup sheet 90. There is one upper heating plate in each heatingsubstation. That is, the heating substations 271, 272, 273, 274, 275,276, 277, and 278 each have a single, upper heating plate 281, 282, 283,284, 285, 286, 287, and 288, respectively.

[0153] Beneath the sheet 90, each of the heating substations 271-278includes a two or more bottom heating plates arranged across the widthof the sheet 90 to define a group (group 301 in heating substation 271,group 302 in heating substation 272, group 303 in heating substation273, group 304 in heating substation 274, group 305 in heatingsubstation 275, group 306 in heating substation 276, group 307 inheating substation 277, and group 308 in heating substation 278).

[0154]FIG. 9 is a simplified schematic illustration of the heatingstation 170 which includes the eight heating substations 271-278comprising the upper heating plates 281-288, respectively, and thebottom heating plate groups 301-308, respectively.

[0155] The upper heating plates 281-284 are moved upwardly anddownwardly by a suitable hydraulic piston/cylinder actuator 310. Theupper heating plates 285-288 are similarly moved upwardly and downwardlyby an actuator 312. Actuators 314 and 316 are employed to extend andretract the lower heating plate groups 301-304 and 305-308,respectively.

[0156] When the upper and lower heating plates are extended to contactthe container sheet 90, twenty-four areas of the sheet are heated. Inorder to heat the sheet 90 sufficiently as it is indexed through themachine, the sheet is sequentially heated at each of the heatingsubstations 171-178. The thermal energy of the sheet 90 thus increasesas the sheet 90 is indexed through the heating station 170. If the sheet90 has the composition and structure of the preferred embodimentdescribed above with reference to FIG. 2, then the heating station 170preferably functions to heat the twenty-four areas of the sheet 90 to afinal temperature in the range of between about 160° C. and about 167°C.

[0157] As shown in FIG. 9, each upper heating plate 291-299 hastwenty-four heating pads 400 arranged as shown in FIG. 9. The heatingpads 400 are arranged on each plate 281-288 in six rows orientedlengthwise along the length of the machine 157 in the feed direction ofthe container sheet 90. Each of the six rows has four heating pads 400.The six rows are arranged in pairs, and the spacing between adjacentpairs is slightly greater than the spacing between the two adjacent rowsin each pair. This is necessary to ensure proper alignment relative tothe strip regions 54 in the lid sheet 92 and to the wider spacingbetween the strip regions 94 in the lid sheet 92 (see FIG. 4).

[0158] As illustrated in FIGS. 9A and 10, each pad 400 has an ovalconfiguration. Each pad is preferably formed as a unitary part of theassociated plate and projects outwardly from the surface of the plate.Each pad has the same size and configuration. The minor axis of the ovalis larger than the diameter of the largest transverse section of theportion of the container to be thermoformed (i.e., larger than thediameter of the container body wall 74 (FIG. 1)). The pads 400 areoriented with the axis of the major diameter aligned in the machinedirection (i.e., parallel to the advancement direction of the containersheet 90 through the machine 157).

[0159] The oval configuration of each heating pad 400 results in theheating of a larger area of the sheet which is to be formed into acontainer (by the thermoforming process as described in detailhereinafter). The larger area, especially along the major axis of theoval configuration, accommodates some misalignment of the containersheet 90 as it is indexed to advance through the machine 157. However,even the minor axis dimension of the oval is preferably larger than theoutside diameter of the container body wall 74 that is to bethermoformed, and thus the oval configuration of each heating pad 400also accommodates some transverse misalignment of the sheet 90.Consequently, even though the sheet 90 may be misaligned as it advancesthrough the machine 157, a sufficiently large area of the sheet 90 isheated for thermoforming each container so that the container can beformed anywhere within that larger oval area (which is at the desired,elevated temperature necessary for proper container formation). In thepreferred embodiment where it is intended for the container to have thestructure and dimensions described above with reference to TABLE 2, thepad major axis is 79 mm., and the pad minor axis is 75 mm.

[0160] The bottom heating plate groups 301-308 are schematicallyillustrated in FIG. 9. The lower heating plate group 301 at the upstreamend of the heating station 170 has a back plate 301B and a front plate301F arranged transversely across the sheet processing path of themachine 157 in registry below the overlying top heating plate 381. Eachplate 301B and 301F includes twelve oval pads 400 arranged in three rowsof four pads 400 each. The three rows are aligned along, and parallelwith, the sheet processing path. The transverse or lateral spacingsbetween the rows of pads 400 correspond to, or match, the transversespacings of the rows of pads 400 in the top heating-plate 181.

[0161] The next downstream bottom heating plate group 302 is identicalwith the above-described bottom heating plate group 301, and the group302 includes a back heating plate 302B and a front heating plate 302F.

[0162] The next heating plate group 303 is also identical with the firstbottom heating plate group 301, and the group 303 includes a backheating plate 303B and a front heating plate 303F.

[0163] The next bottom heating plate group 304 is also identical withthe first bottom heating plate group 301, and the group 304 includes aback heating plate 304B and a front heating plate 304F.

[0164] The bottom sets of heating plates 301, 302, 303, and 304 may becharacterized as together defining a first set of heating platesarranged in pairs, with each pair of heating plates of the first setbeing vertically aligned with a different one of the top heating plates181, 182, 183, and 184. The first set of four groups of heating platepairs is designated in FIG. 9 by the reference number 402.

[0165] Downstream of the first set 402 of heating plates is a second setof heating plates 406. The second set 406 includes three groups ofheating plates 305, 306, and 307. Each group 305, 306, and 307 includesthree separate heating plates. In particular, group 305 includes a backheating plate 305B, a center heating plate 305C, and a front heatingplate 305F.

[0166] Each heating plate 305B, 305C, and 305F has eight, unitary, ovalheating pads 400 arranged in two rows of four pads each. The rows up arespaced to match, or correspond with, the rows of heating pads in the topheating plate 285.

[0167] The three heating plates in the next downstream adjacent group306 include a back heating plate 306B, a center heating plate 306C, anda front heating plate 306F. These plates are identical with the plates305B, 305C, and 305F, respectively, discussed above.

[0168] The third group 307 includes a back heating plate 307B, a centerheating plate 307C, and a front heating plate 307F. These heating plateshave the same structure as the above-described other plates in the plategroups 305 and 306.

[0169] The second set 406 of bottom heating plates (deemed by the groups305, 306, and 307) may be characterized as being located relative to thefirst set 402 at a downstream location along the sheet processing path.The second set 406 of bottom heating plates may be further characterizedas being arranged in groups of three heating plates, with each group ofthree heating plates being vertically aligned with a different one ofthe top heating plates (i.e., top heating plates 285, 286, and 287).

[0170] A third set of heating plates is designated in FIG. 9 by thereference number 408. The third set or heating plates 408 includes justone heating plate group 308. The heating plate group 308 includes a backheating plate 308B and a front heating plate 308F. The structure of theheating plates 308B and 308F is identical to the structure of the firstgroup heating plates 301B and 301F, respectively, described above.

[0171] The third set 408 of heating plates may be characterized as beinglocated relative to the second set 406 at a downstream location alongthe sheet processing path. The third set 408 may be furthercharacterized as being arranged in at least one pair vertically alignedwith a different one of the top heating plates (i.e., top heating plate288). The number of pairs of heating plates in the third set 408 is lessthan the number of pairs of heating plates in the first set 402.

[0172] The above-described configuration of bottom heating platespermits the container sheet 90 to be heated in a manner that can be morecarefully controlled. Specifically, to heat the sheet 90, the top andbottom heating plates are closed to contact the top and bottom surfaces,respectively, of the sheet 90. This heats the sheet by directconduction.

[0173] In the preferred method of operation, the heating plates areclosed in clamping engagement around the sheet 90 for about 3.3 secondsif the sheet 90 has the preferred structure and dimensions describedabove with reference to FIG. 2.

[0174] After the 3.3 second heating step, the top and bottom heatingplates are retracted. The sheet 90 is then indexed so as to advance thesheet. The portion of the sheet 90 that was heated between the topheating plate 281 and the underlying bottom heating plates 301B and 301Fis thus advanced so that it is located between the second top heatingplate 282 and the underlying bottom heating plates 302B and 302F. Thetop and bottom heating plates are again closed for a 3.3 second heatingcycle. This operation sequence is repeated through all of the eightheating substations (i.e., heating substation 271-278).

[0175] At each heating substation 271-278, the oval container areas ofthe sheet 90 between the top and bottom heating plates asborb morethermal energy. Thus the temperature of the sheet oval areas increaseswith successive advancement of the sheet through the heating station170.

[0176] It has been found that the regions of the sheet 90 between theoval areas heated by the pads 400 also increase in temperature owing tolateral conduction of heat through the sheet 90. Further, as the sheetprogresses through the machine, the sheet 90 is subjected generally toincreasing temperatures from the atmosphere within the heating station170. The temperature of the atmosphere within the heating station 170increases with increasing distance inwardly from the inlet end of theheating station. However, the temperature of the internal atmosphere atthe last the heating substation 278 may drop somewhat because it isadjacent the exterior end of the heating station 170.

[0177] In order to compensate for the tendency of the sheet 90 to beheated too quickly and/or too much as it progresses through the heatingstation 170, the temperature of the bottom heating plate; can beindividually controlled. Preferably, the bottom heating plates, as wellas the top heating plates, are electrically heated. Suitable electricalcontrol systems, the details of which form no part of the presentinvention, are provided for controlling the temperature of each heatingplate in response to temperature data transmitted from appropriatesensors in the machine heating station 170.

[0178] In the first half of the heating station 157, the temperatureacross the width of the sheet 90 can be adequately controlled with justtwo, separate, bottom heating plates and one top heating plate in eachsubstation 271-274. Accordingly, the heating plates in the set 402 inthe first half of the bottom heating station 170 are arranged in pairsin each group 301-304. Each plate of a pair can be controlled separatelyfrom the adjacent plate of that pair.

[0179] However, it has been found to be desirable to have more controlover the temperature of the sheet 90 across the width of the sheet inthe downstream half of the heating station 170, and particularly in thearea of the bottom heating plates comprising the set 406. Thus, in thebottom heating plate set 406, each group of heating plates 305-307includes three heating plates across the width of the container sheet90. The temperature of each of the three heating plates in each of thesegroups can be separately controlled.

[0180] In the last bottom heating plate set 408 adjacent the dischargeend of the heating station 170, it has been found to be sufficient toprovide, and to separately control, only two heating plates across thewidth of the sheet 90.

[0181] It has also been determined that the top heating plates 281-288can each remain as single, unitary plate which are each controlled to adesired temperature across the entire width of the sheet 90. Anytemperature differences across the width of the sheet 90 can beaccommodated by control of the bottom heating plates which include thetwo or three separately controllable, bottom heating plates across thewidth of the web.

[0182] Because the cost and complexity of the system increases with anincreasing number of separately controllable heating plates, it has beenfound that the above-described system is advantageous in that the eighttop heating plates 281-288 in each substation can each be maintained asa single heating plate rather than being replaced by two or more heatingplates.

[0183] It will also be appreciated that the bottom, two-and three-plategroups 301-308 would be employed on the top of the machine, and the top,single heating plates 281-288 could be provided on the bottom of themachine. Of course, the particular temperatures to which the plates insuch a modified system would be controlled might be somewhat differentowing to upward convective transfer of heat through the internalatmosphere within the heating station 170 and owing to other factors.

[0184] Typically, the marginal sections of the sheet 90 and some of theinternal mechanisms in the heating station 170 are cooled withappropriate gas flow. The cooling systems, the sterilizing atmospheresystem, the mechanisms for extending and retracting the heating plates,and the detailed design and operation of the temperature control systemfor the heating plates form no part of the present invention.

Forming the Container

[0185] After the heated container sheet 90 leaves the heating station170, the sheet 90 is indexed through the thermoforming station 180. Herea plurality of plugs are lowered into the sheet to deform the sheetdownwardly into die cavities which each have the configuration of theexterior of the formed container. Compressed air is injected over thesheet 90 to blow the sheet outwardly away from the plugs and against thewalls of the die cavities. The process and apparatus for thermoformingthe containers as thus far generally described is conventional and formsno part of the present invention. However, one aspect of the presentinvention involves the specific design of the shape of the forming plugwhich is illustrated in FIGS. 11 and 12.

[0186] The plug is designated generally by the reference number 450 inFIGS. 11 and 12. There are twenty-four such plugs 450 which correspondto the twenty-four heated oval areas in the sheet 90. Each plug 450 hasan end 451 defining an opening 452. End 451 is constructed to engage anddeform sheet 90. In the preferred embodiment of the present invention,end 451 is positioned vertically above sheet 90. The plug 450 isextended downwardly and retracted upwardly by operation of the actuatorsuch that end 451 deforms sheet 90 in a downward direction. The detaileddesign and operation of such an actuator forms no part of the presentinvention relating to the plug contour.

[0187] The plug 450 includes an end 453 having a central opening 460surrounded by a frustoconical surface 462, a flat, annular surface 464,a cylindrical surface 466, an annular shoulder 468, and an angled,frustoconical corner surface 470. The plug 450 also has a cylindricalside surface 472 which merges with an upper arcuate surface 474.

[0188] The dimensions of the preferred embodiment of the thermoformingplug 450 are listed below in Table 4 with reference to the dimensiondesignations shown in FIG. 12.

[0189] The finish of the exterior surfaces of the plug 450 is smooth.The smooth surface finish, in conjunction with the particular exteriorconfiguration, is highly effective in establishing proper contact withthe sheet. This facilitates the proper stretching of the sheet 90 intothe die cavity which facilitates the creation of the desired wallthickness profile in the container. The shape and finish of the plug 450also permits the sheet 90 to be uniformly released from the plug andblown against the die by the injected compressed air.

[0190] The preferred embodiment of the plug 450 has been found to workextremely well with the preferred embodiment of the sheet 90 having thestructure and composition described above with reference to FIG. 2. Thepreferred embodiment of the plug 450 is maintained within an appropriatetemperature range during operation of the machine 157 go as tofacilitate the proper contact between the plug 450 and sheet 90 and soas to facilitate subsequent disengagement of the sheet 90 from the plug450. Table 4 below identifies the dimensions of the preferred design ofthe plug 450 illustrated in FIG. 12 with reference to the dimensiondesignations identified in FIG. 12. TABLE 4 Thermoforming Plug DimensionNominal Designation Dimension A 40 mm. B 60 mm. C 1.9 mm. D 6 mm. E 83.5mm. F 99 mm. G 100 mm. H 45 mm

Sealing the Lid Sheet to the Container Sheet

[0191] After the cups or containers have been formed in the sheet 9O bythe plugs 450, the sheet is indexed to the lid sealing station 200. Theformed sheet 90 moves below, but in registration with, the lid sheet 92which is advancing from the hydrogen peroxide sterilizing station 220into the sealing station 200.

[0192] In the sealing station 200 there are twenty-four lid heat sealingtools 500 (FIGS. 13, 14 and 15). Each of the twenty-four heat sealingtools 500 is adapted to engage a generally circular area of the lidsheet 92 and force it with the underlying container sheet 90 against avertically reciprocable member 510 around the periphery of each formedcontainer body.

[0193] As shown in FIG. 13, each sealing tool 500 has a generallyannular sealing face. FIG. 14 shows the tool sealing face crosssectional profile which is uniform circularly around the tool except intwo areas where the profile is altered by two recesses 514 (FIG. 13 and15). When the lid seal tool 500 is used to seal the preferred lid sheet92 (having the preferred composition and structure described above withreference to FIG. 5) to the preferred embodiment of the container sheet90 (described above with reference to FIG. 2), the sealing toolpreferably has the dimensions set forth in Table 5 below with referenceto the dimension designations in FIG. 14. TABLE 5 Lid Seal Tool Lid SealTool Dimension Dimension Designation (mm.) A 69.0 B 0.7 C 1.2 D 4.1 E0.5 F 0.6 G 0.5 H 0.5 I 0.2 J 0.2 K 0.3

[0194] With reference to FIG. 14, the sealing tool 500 includes aninner, annular relief surface 520. Adjacent the relief surface 520 is aflat sealing surface defined at the bottom of a downwardly projecting,annular ring 530. At the outer edge of the ring 530 is an upwardlyextending annular groove 540 which is open downwardly. Extendingradially outwardly from the groove 540 is a flat, outer, annular reliefstep surface 550.

[0195] When the sealing station is actuated, each sealing tool 500 isextended downwardly at the same time the support member 510 is extendedupwardly so as to press the lid sheet 92 and container sheet 90 betweenthe tool 500 and support member 510.

[0196] The support member 510 includes twenty-four apertures 512 foreach receiving the portion of the container which projects downwardlyfrom the thicker, horizontally disposed sheet 90 which is supported onthe top surface of the support member 510. An annular portion of thehorizontal sheet 90 adjacent the aperture 512 will ultimately beseparated from the rest of the sheet 90 (as at radius 561 in FIGS. 14and 15) to form the flange of the container (i.e., flange 70 as shown inFIG. 3).

[0197] When the lid sheet 92 and container sheet 90 are squeezed betweenthe support member 510 and sealing tool 500, a seal structure is formedwith the unique configuration as described above in detail withreference to FIG. 6 which shows the completed seal.

[0198] The sealing tool 500 is electrically heated to a temperatureranging between about 245° C. and about 255° C. When the preferred lidsheet 92 (having the preferred composition and structure described abovewith reference to FIG. 5) is sealed to the preferred container sheet 90(having the preferred composition and structure described above withreference to FIG. 2) with the preferred form of the tool 500 describedabove with reference to Table 5, then the sheets 90 and 92 arepreferably squeezed together with a force of between about 85 and about105 kilonewtons for a period of time ranging between about 1.8 and about1.9 seconds. This provides a strong seal that has a high burst strengthand that has the configuration shown in FIG. 6.

[0199] It will be appreciated that the inner, annular relief surface 520and the annular groove 540 of the sealing tool 550 accommodate upwarddeformation of the sheet material (as at bulge 140 and bulge 142 shownin FIG. 6) as the ring 530 creates the recessed region in the seal(i.e., the region 138 as shown in FIG. 6). This results in the formationof the upset beads 131 and 133 in the lid flange 70 (as seen in FIG. 6).This also accommodates the lateral displacement of the bottom layers 105and 104 of the lid material to form the beads 132 and 134 (as seen inFIG. 6). This also accommodates the formation of the high strength,leak-tight heat seals 121 and 122 between the beads 131 and 132, andbetween the beads 133 and 134, respectively.

[0200] It will be noted that the sealing tool 500 has a relatively wide,annular surface 550 outwardly of the groove 540. The surface 550 isalmost four times wider than the surface of the ring 530. The widesurface 550 facilitates the transfer of a large amount of thermal energyinto the underlying sheets 90 and 92. Tho additional thermal energycontributing to the creation of robust heat seals 121 and 122 atworkable operating ranges.

[0201] Because the outer, peripheral surface 550 is higher than thesurface of the projecting ring 530, the pressure on the sheets 90 and 92under the surface 550 is considerably less than the pressure exerted bythe projecting ring 530. This prevents the creation of a full,high-strength seal between the sheets 90 and 92 under the tool outer,annular surface 550. The sheets 90 and 92 in this area are only lightlybonded or tacked. The lightly bonded or tacked region extends radiallyoutwardly beyond the outer edge of the cup flange that will besubsequently defined when the package is severed from the two sheet atthe die cutting station 230. The die cutting apparatus will cut the lidand flange out of the two sheets in the lightly bonded or tacked regionwhich is created under the radially outer, annular region of the toolsurface 550.

[0202] The unique profile of the sealing tool 500 illustrated in FIGS.13-14 produces a heat seal connection of the lid 40 to the containerflange 70 which is substantially devoid of wrinkles in the lid material.The seal is relatively strong, and yet the seal still permits thelift-up tab 42 in the finished package to be free of any bonding to theunderlying portion of the lid 40.

[0203] Because the seal structure produced with the sealing tool 500prevents, or substantially minimizes, the production of wrinkles in thelid material, there are no channels or passages created through theannular heat seals which could result in leakage or which couldotherwise deleteriously affect the integrity of the seals.

[0204] The recesses 514 in two areas of the face of the sealing tool 500are aligned along the lid tab hinge 96 (FIGS. 4, 5, 16, and 17). Therecesses 514 are located radially on the tool 500 so as to extendinwardly beyond what will become the outer edge of the lid. Thus, withreference to FIG. 16, an inner portion of each recess 514 in the tool500 results in the creation of the peripheral areas 151. Because thetool recessed areas 514 prevent the application of pressure to the areaof the lid in the regions 151, each region 151 is bonded only verylightly or not at all. This permits the user to more easily open the lidby pulling up on the tab 42 as shown in FIG. 17 and as previouslydescribed in detail with reference to FIG. 17.

[0205] During operation of the heat sealing station 220, the supportmember 510 and the heat sealing tools 500 are reciprocated toward andaway from each other by suitable conventional mechanisms in the machine157, the details of which mechanisms form no part of the presentinvention. The electrical heating system for the tools 500 and thecontrols for the electrical heating system may include any appropriatedesign and or modification of conventional systems in the machine 157.Accordingly, the detailed design and operation of such systems form nopart of the present invention.

Die-Cutting the Container

[0206] After the sheets 92 and 90 are sealed together in the sealingstation 220, the seled assembly is advanced to the die-cutting or trimstation 230. The die-cutting station 230 includes twenty-four punch anddie tool sets, two of which are shown in FIG. 18 wherein they aredesignated generally by the reference number 600. Each tool set 600includes a punch 604 and a die 610.

[0207] During operation of the die-cutting station 230, the punches 604and the dies 610 move toward and away from each other by suitablemechanisms (not illustrated). These may be of any appropriateconventional or special design, the details of which form no part of thepresent invention.

[0208] Each punch 604 has a generally cylindrical, lower outer surface620 terminating in a bottom, distal edge 622. The punch 604 has afrustoconical inner surface 626 which intersects the exteriorcylindrical surface 620 at the distal end 622. In the preferredembodiment, the frustoconical surface 626 defines an included angle ofabout 44.43 degrees with respect to the surface 620. This provides anacute angle peripheral cutting edge at the bottom end 622. The diameterof the cutting edge bottom end 622 is substantially equal to the outerdiameter of the container flange that is to be defined when thecompleted package is severed from the sheets 92 and 90 by the punch.

[0209] The die 610 includes an upper support surface 630 and defines anaperture 640 for receiving the portion of the container or cup whichextends downwardly from the sheet 90. Before the sheets 90 and 92 areadvanced forward to bring the formed cups into the die-cutting station230, the dies 610 are in a lowered, retracted position so that thedownwardly projecting containers can be advanced over the dies and intoa position in registration with the apertures 630. Subsequently, whenthe die-emitting station 220 is operated, the dies 610 move upwardlyaround the downwardly projecting container to engage the bottom surfaceof the portions of the sheet 90 extending between the containers. Thisoccurs at the same time that the punches 604 are extended downwardlyinto the sheets 92 and 90.

[0210] The preferred embodiment of the punch and die set 600 is designedfor cutting the preferred lid sheet 92 (having the preferred structureand composition described above with reference to FIG. 5) and to cuttingthe preferred container sheet 90 (having the preferred structure andcondition described above with reference to FIG. 2). In the preferredembodiment of the punch and die set 600, the aperture 640 in the die 610is sufficiently large to provide a radial clearance C (FIG. 19) of about0.2 inch between the exterior cylindrical surface 620 of the punch 604and the interior surface of the die 610. Also, in the preferredembodiment of the punch and die set 600, the punch cutting edge projectsdownwardly a distance B (FIG. 19) which is preferably about 0.3 inch.The preferred peripheral cutting edge acute angle D is about 44.43degrees. The preferred radius A is about 1 inch.

[0211] As the punch 604 and die 610 are moved toward each other, thepunch cuts into the sheets 92 and 90 and severs the package from theremaining peripheral portion of the sheets 92 and 90. The punch 604 cutsthrough the sheets 92 and 90 in the area of the connection between thelid sheet 92 and container sheet 90 which is only lightly bonded, andthis is the radially outwardly portion of the region 150 described abovewith reference to FIG. 6.

[0212] Preferably, both the die and the punch are cooled by conventionalsystems (the details of which form no part of the present invention) soas to keep the temperature of the punch and die within about 5° C. ofeach other. This prevents differential expansion which might createinterference.

[0213] During the operation of the punch and die it is preferred tomaintain some amount of tension on the sheets 92 and 90. The punch 604and die 610 are operated so that they both move along a line of actionthat is substantially perpendicular to the plane of the sheets 92 and90.

[0214] The preferred form of the punch and die set 600, when operatedaccording to the preferred process as described above, creates a veryclean, smooth cut around the peripheral edge of the package lid 40 andcontainer flange 70 (FIG. 1). This compares very favorably with other,conventional punch and die set apparatus and processes which do notproduce a very clean and smooth edge on materials such as polypropylene.Such other apparatus and processes typically create filaments ofmaterial hanging from the area of the cut edge, and these are typicallyreferred to as “filaments,” “angel hairs,” “strands,” or “stringers”.These are not desirable, especially when it is intended that a user willdrink from the open cup. The package created with the punch and die set600 of the present invention substantially minimizes, or eliminates thecreation of such angel hairs or filaments.

[0215] It will be readily apparent from the foregoing detaileddescription of the invention and from the illustrations thereof thatnumerous variations and modifications may be effected without departingfrom the true spirit and scope of the novel concepts or principles ofthis invention.

What is claimed is:
 1. A sealed package comprising; a container having a body defining a mouth and having a flange around said mouth; and a lid disposed on said container across said mouth and flange, said flange having an annular, upset first bead of a heat-sealable thermoplastic material, said lid having an annular second bead of a heat-sealable thermoplastic material adjacent said first bead, said first and second beads being sealed together with a first heat seal comprising a resolidification of a melted interface portion of said first and second beads.
 2. A sealed package in accordance with claim 1 , wherein: said flange has an annular, upset third board of a heat-sealable thermoplastic material; said lid has an annular fourth bead of a heat sealable thermoplastic material adjacent said third bead; and said package includes a second heat seal comprising a resolidification of a melted interface portion of said third and fourth beads.
 3. A sealed package in accordance with claim 2 , wherein said first and third beads are spaced apart and are located between said second and fourth beads.
 4. A sealed package in accordance with claim 2 , wherein said lid is sealed to said flange outwardly of said lid fourth bead in a substantially annular configuration extending from said fourth bead to an outer edge of said flange.
 5. A sealed package in accordance with claim 2 , wherein said flange is deformed between said first and third beads to define a recess receiving a downwardly projecting portion of said lid.
 6. A sealed package in accordance with claim 2 , wherein said lid defining an upwardly projecting portion above said second bead and an upwardly projecting portion above said fourth bead.
 7. A sealed package in accordance with claim 6 , wherein said lid is deformed between said upwardly projecting portions of said lid to define an annular recess on an exterior of said lid.
 8. A sealed package in accordance with claim 2 , wherein said lid comprises a heat sealable material, and wherein said second and third beads are formed from a lateral displacement of said heat sealable material.
 9. A container formed from a sheet material, said container comprising a unitary structure of said sheet material, said container further comprising: peripheral flange defining an opening; a downwardly and inwardly tapering hollow body defined around a longitudinal axis by a generally annular sidewall extending downwardly from said flange; a bottom wall comprising: (1) an annular, curved, peripheral base extending from a lower end of said body sidewall, said base constructed to engage a flat support surface along a generally circular line of contact; (2) an annular first end wall extending from said annular curved, peripheral base both inwardly and toward said opening defined by said flange; (3) an annular second end wall located closer to said opening than said first end wall and extending from said first end wall both inwardly and toward said opening defined by said flange; and (4) a central, third end wall located closer to said opening defined by said flange than said second end wall and extending from said second end wall.
 10. A container in accordance with claim 9 , wherein said first end wall defines a substantially frustoconical exterior surface.
 11. A container in accordance with claim 9 , wherein a thickness of said sidewall increases with increasing distance from said flange toward said base.
 12. A container in accordance with claim 9 , wherein said sidewall tapers at an angle of between about 1.8 degrees and about 3.2 degrees relative to said longitudinal axis.
 13. A container in accordance with claim 9 , wherein said sheet material comprises: a plurality of layers of material co-extruded together to form a multi-ply sheet comprising first, second, third, fourth, and fifth layers, said sheet first layer adapted for functioning as an exterior side of the container and comprising polypropylene, said second layer functioning as an adhesive joining said first and third layers, said third layer functioning as an oxygen barrier and comprising ethylene vinyl alcohol, said fourth layer functioning as an adhesive joining said third and fifth layers, and said fifth layer adapted for functioning as an interior side of the container and comprising polypropylene.
 14. A container in accordance with claim 9 , wherein said second end wall defines an angle of about 45 degrees relative to said longitudinal axis.
 15. A container formed from a sheet material, said container comprising a unitary structure of said sheet material, said container further comprising: a peripheral flange defining an opening; a downwardly and inwardly tapering hollow body defined around a longitudinal axis by a generally frustoconical annular sidewall extending downwardly from said flange; a bottom which includes an annular, curved, peripheral base extending from a lower end of said body sidewall, said sidewall increasing in thickness with increasing distance from said opening.
 16. A container in accordance with claim 15 , wherein said sidewall defines a generally frustoconical exterior surface defining an angle between about 1.8 degrees and about 3.2 degrees relative to said longitudinal axis.
 17. A container in accordance with claim 15 , wherein said sheet material comprises: a plurality of layers of material co-extruded together to form a multi-ply sheet comprising first, second, third, fourth, and fifth layers, said sheet first layer adapted for functioning as an exterior side of the container and comprising polypropylene, said second layer functioning as an adhesive joining said first and third layers, said third layer functioning as an oxygen barrier and comprising ethylene vinyl alcohol, said fourth layer functioning as an adhesive joining said third and fifth layers, and said fifth layer adapted for functioning as an interior side of the container and comprising polypropylene.
 18. A container formed from a thermoplastic sheet material, said container comprising a unitary structure of said sheet material, said container further comprising: a peripheral flange defining an opening; a downwardly and inwardly tapering hollow body defined around a longitudinal axis by a sidewall extending downwardly from said flange; and a bottom defined by (1) an annular, peripheral base extending from a lower end of said body sidewall, and (2) an end wall structure that extends radially inwardly from said peripheral base and that is located closer to said opening than is said peripheral base.
 19. A container in accordance with claim 18 , wherein said first end wall defines a substantially frustoconical exterior surface.
 20. A container in accordance with claim 18 , wherein said sidewall defines a generally frustoconical exterior surface defining an angle between about 1.8 degrees and about 3.2 degrees relative to said longitudinal axis. 